Electric power conversion device, motor driving device, and refrigeration cycle application apparatus

Abstract

An electric power conversion device is a device for supplying an output voltage to a load from output terminals, and includes a rectifier circuit to rectify an AC voltage and to output the rectified voltage, a booster circuit to supply the output voltage to the output terminals, a voltage detector to output a voltage detection value indicating the output voltage, and a controller. The booster circuit includes a reactor connected to the rectifier circuit, a smoothing capacitor to smooth the rectified voltage, thereby generating the output voltage, and a switching element to short-circuit the reactor. The controller controls a conduction period of the switching element based on the voltage detection value so that a first pulsation frequency which is a frequency of pulsation of the output voltage is higher than a second pulsation frequency which is a frequency of pulsation of the rectified voltage.

1 . An electric power conversion device for supplying an output voltage to a load from output terminals, comprising:
 a rectifier circuit to rectify an AC voltage and to output a rectified voltage;   a booster circuit to supply the output voltage to the output terminals;   a voltage detector to detect the output voltage and to output a voltage detection value indicating the output voltage; and   a controller, wherein   the booster circuit has
 a reactor connected to the rectifier circuit, 
 a smoothing capacitor to smooth the rectified voltage, thereby generating the output voltage, and 
 a switching element to short-circuit the reactor during a conduction period which is a period of an ON state of the switching element, and 
   the controller controls the conduction period of the switching element based on the voltage detection value so that a first pulsation frequency which is a frequency of pulsation of the output voltage is higher than a second pulsation frequency which is a frequency of pulsation of the rectified voltage.   
     
     
         2 . The electric power conversion device according to  claim 1 , wherein the controller
 controls the conduction period for times when the voltage detection value is less than or equal to a predetermined threshold value so as to bring an average value of the voltage detection value close to a predetermined target voltage, and   controls the conduction period for times when the voltage detection value is over the threshold value so that the conduction period becomes shorter than the conduction period for times when the voltage detection value is less than or equal to the threshold value.   
     
     
         3 . The electric power conversion device according to  claim 2 , wherein
 when the voltage detection value is less than or equal to a predetermined threshold value, the controller controls a duty of the switching element so as to bring the average value of the voltage detection value close to the target voltage, and   when the voltage detection value is over the threshold value, the controller executes control by use of a predetermined first duty lower than the duty so as to bring the average value of the voltage detection value close to the target voltage.   
     
     
         4 . The electric power conversion device according to  claim 3 , wherein the first duty is 0. 
     
     
         5 . The electric power conversion device according to  claim 2 , wherein the threshold value is equal to the target voltage or the average value of the voltage detection value. 
     
     
         6 . The electric power conversion device according to  claim 1 , wherein the controller
 performs PI control on the conduction period so as to bring the voltage detection value close to a predetermined target voltage, and   executes control so that a gain of the PI control when the voltage detection value is over a predetermined threshold value is higher than a gain of the PI control when the voltage detection value is less than or equal to the threshold value.   
     
     
         7 . The electric power conversion device according to  claim 6 , wherein the controller has an upper/lower limit limitation unit to control a duty commanding the conduction period of the switching element, to be greater than or equal to a predetermined lower limit value and less than or equal to a predetermined upper limit value. 
     
     
         8 . The electric power conversion device according to  claim 6 , wherein the threshold value is equal to the target voltage or an average value of the voltage detection value. 
     
     
         9 . A motor driving device comprising:
 the electric power conversion device according to  claim 1 ; and   an inverter to convert the output voltage to an AC voltage and to supply the AC voltage to a motor.   
     
     
         10 . A refrigeration cycle application apparatus comprising:
 the motor driving device according to claim  9 ; and   a refrigeration cycle device having a motor driven by the motor driving device.